The package Fuzzy is meant to solve common problems with floating-point
numbers in a systematic way:

Comparing two numbers that are "supposed" to be identical, like
1.0 and 2.1/(1.2+0.9) is not guaranteed to give the
intuitive result.

Rounding a number that is halfway two integer numbers can cause
strange errors, like int(100.0*2.8) != 28 but 27

The Fuzzy package is meant to help sorting out this type of problems
by defining "fuzzy" comparison procedures for floating-point numbers.
It does so by allowing for a small margin that is determined
automatically - the margin is three times the "epsilon" value, that is
three times the smallest number eps such that 1.0 and 1.0+$eps
canbe distinguished. In Tcl, which uses double precision floating-point
numbers, this is typically 1.1e-16.

The problems that can occur with floating-point numbers are illustrated
by the test cases in the file "fuzzy.test":

Several test case use the ordinary comparisons, and they
fail invariably to produce understandable results

One test case uses [expr] without braces ({ and }). It too
fails.

The conclusion from this is that any expression should be surrounded by
braces, because otherwise very awkward things can happen if you need
accuracy. Furthermore, accuracy and understandable results are
enhanced by using these "tolerant" or fuzzy comparisons.

Note that besides the Tcl-only package, there is also a C-based version.

This document, and the package it describes, will undoubtedly contain
bugs and other problems.
Please report such in the category math :: fuzzy of the
Tcllib Trackers.
Please also report any ideas for enhancements you may have for either
package and/or documentation.